Recently, a mobile phone having a camera function is spread in a market, and image information taken by using the camera function of the mobile phone can be transmitted as digital data without change.
It is convenient to take a picture by using only the mobile phone having the camera function without an independent camera. However, there is such a risk that even a place in which taking pictures is inhibited is unfairly shot.
For example, a research institute and a factory including up-to-date facilities have equipments that have to be managed confidentially to outside. Thus, it is sometimes inhibited to take pictures in such places.
Also, it is sometimes inhibited that the audience take pictures by using cameras in a concert hall.
However, there can be such a method that visitors to the research institute and the up-to-date factory facilities and the audience visiting the concert hall are forced to temporarily deposit their own mobile phones at entrances of the places in which taking-picture and phone call are inhibited. At this time, there is such an information security problem that they sneak a look at information stored in the deposited mobile phones. In addition, as for the concert hall, there is such a problem that, since a large number of audience visit the hall, it takes too much time and labor to perform the management of the temporarily deposited mobile phones. Therefore, the method is not a practical solution.
As a background art, there is disclosed a technique of a mobile phone capable of switching a mode thereof in passing through an entrance gate (e.g., see Japanese Patent Applications Laid-open under No. 2003-69670).
However, in the case of the mobile phone having the camera function, even if the mode thereof is switched, it is possible to secretly take a picture unless the power thereof is switched off. Therefore, it becomes possible that the place in which taking-picture is inhibited is problematically shot.